Obesity, as a disease, affects a significant portion of the world's population. Obesity often leads to multiple chronic medical conditions and premature death from cardiovascular events and cancer. The U.S. Centers for Disease Control and Prevention (“CDC”) reports that over 33% of the U.S. population is obese, with a body mass index (“BMI”) of over 30, and another 35-40% of the population is overweight, with a BMI of 25-30. The CDC reports that the percent of the population being either overweight or obese by 2018 will be 75%. The CDC also reports that obesity directly costs the U.S. economy $147 billion currently, and projects that the costs will approach $315 billion by 2020. The increase in obesity and the financial impact on the local economy is not limited to the United States but impacts many countries throughout the world.
Obesity has environmental, genetic, and behavioral origins but is intractable to most medical and behavioral interventions. Weight loss, or bariatric, surgery seems to be the only effective long-term treatment option for patients with a BMI greater than 35. Despite the 20 million patients who are eligible for weight loss surgery in the United States, the number of procedures per year has plateaued at about 200,000, essentially eliminating any meaningful public health effect of the surgery.
In recent years, laparoscopic vertical sleeve gastrectomy has emerged as a procedure that is safe and effective for patients who are eligible for weight loss surgery. Laparoscopic surgery is a form of minimally invasive surgery inside of the abdominal cavity performed at a distance by the surgeon. Laparoscopic surgery instrumentation is designed to fit through small incisions in the abdominal wall, typically 5 mm to 15 mm in diameter. The abdominal access sites are maintained by cannulae, or trocars, that are designed to maintain pressure in the abdominal cavity with valves that seal around an instrument shaft. Videoscopic guidance may be used throughout the surgery. Since its introduction in 2003 as a stand-alone surgery, vertical sleeve gastrectomy has been studied extensively. It is now widely accepted as the surgery that should be offered to most morbidly obese patients over laparoscopic adjustable gastric banding and laparoscopic Roux-en-Y gastric bypass. The surgery has been adopted by most bariatric surgeons and is now one of the most commonly used procedures to achieve effective weight loss.
During a vertical sleeve gastrectomy, approximately 80% of the stomach is removed and the remaining pouch is based on the less distensible lesser curve of the stomach. The fundus of the stomach, which is formed by the upper curvature of the organ, is the most crucial portion of the stomach that is removed. The resultant gastric pouch generally should be about 80 mL to about 820 mL in volume, should not be narrowed at the incisura angularis, should be as straight as possible to avoid obstruction from spiraling or zigzagging, should be about 0.5 cm to about 2 cm away from the gastroesophageal junction, and should be about 2 cm to about 10 cm away from the pylorus.
A vertical sleeve gastrectomy is typically performed using standard laparoscopic equipment. The greater curvature of the stomach is mobilized by using vessel-sealing devices to seal the gastric branches of the gastroepiploic vessels and the short gastric vessels. The posterior adhesions of the stomach are also divided so the stomach is fully mobilized while the blood supply to the lesser curvature remains intact. The left crus of the diaphragm is an important landmark to ensure the fundus has been fully mobilized.
Following mobilization of the stomach and repair of any hiatal hernia that may be present, a calibration tube or bougie is typically introduced into the stomach through the mouth. The bougie is inserted through the mouth, down the esophagus, and into the stomach, where it is used as a point of reference in order to help align the initial staple fire. The bougie acts as a left-hand landmark, which the surgeon uses to visualize the path of the staple line. A surgeon creating a sleeve gastrectomy staple line will estimate 2.0 cm away from the lesser curvature of the stomach and visually orient the stapler. As constant diameter bougies cannot be used to facilitate orienting the stapler, only surgeon experience and estimation is used. At the top of the staple line, it is important to not divide part of the esophagus or the ‘sling fibers’ of the cardia, which participate in the physiologic anti-reflux action of the lower esophageal sphincter. Surgeons must use visual cues to ensure that the staple line is a safe distance away from the gastroesophageal junction.
Resection is accomplished by a series of applications of a laparoscopic linear surgical stapler, which are also referred to as endocutter surgical staplers. The staplers that are most commonly used for sleeve gastrectomy are no more than 60 mm in length and include an integrated cutting blade, an anvil, and a cartridge, where the anvil and cartridge are parallel in the longitudinal direction. Conventional endocutter staplers have double or triple staggered rows of staples on either side of the cutting blade. Each staple application places two or three staggered rows of staples into the tissue on either side of the cutting blade. For sleeve gastrectomy, the average number of staple fires per procedure is 3 to 7 in order to create a continuous resection line. This results in a resection line that is about 15 cm to about 37 cm on average.
Proper alignment between the anvil and cartridge is very important during staple formation. Surgical staplers must have alignment in the x, y, and z axes to be able to form B-shaped staples. The alignment of the anvil and cartridge must be maintained along the length of the stapler. The anvil may be deflected during staple formation due at least in part to the forces of tissue and staple formation on the anvil. This deflection has limited the lengths of staplers. More specifically, the longer the stapler is, the more the tip of the stapler tends to deflect. This often results in a gap that is too wide to form staples appropriate for the thickness of the tissue to be stapled.
Currently, surgeon training, experience, and trial and error are the only tools used to aid the surgeon in determining the path of the resection line in a vertical sleeve gastrectomy. Only after applying the stapler to begin creating the resection line is the resultant stomach anatomy demonstrated. Before beginning stapling, the surgeon must attempt to envision the resultant anatomy of the stomach. Further, the surgeon must actively and accurately control the stapler during the resection to produce the desired resection line. Because the thickness of the stomach tissue varies at the antrum, the body, and the fundus, different staple leg lengths are typically used. This requires the stapler to be removed from the patient between firings to load the stapler with a new cartridge having staples with an appropriate leg length. Generally, one or more applications of cartridges including staples with a longer closed leg length are followed by one or more applications of cartridges including staples with a shorter closed leg length. This serial cartridge application can lead to a less than optimal anatomic appearance of the segmented staple line, such as a “zig-zagging” or spiraling line.
There is wide variability in the size and type of calibration tube, or bougie, used by surgeons to size the remaining gastric sleeve. Some surgeons use an endoscope (30 French or 1 cm in diameter) while others use a large mercury-weighted bougie (60 French or 2 cm in diameter). In a large meta-analysis, there was no difference in weight loss when bougie sizes of less than 40 and greater than 40 were used. The resection line is important in sleeve gastrectomy because the amount of weight loss and subsequent medical complications may be a direct result of the quality of the resultant anatomy. The resultant anatomy is determined by the staple line created by the surgeon during the gastrectomy. Negative consequences related to the quality of the staple line may include, for example, gastroesophageal reflux, weight loss failure, weight regain, food intolerance, resection line bleed, and leak.
Leaks are the most concerning complication of a vertical sleeve gastrectomy. In large pooled databases, the leak rate is approximately 0.3 to 2%. Leak is thought to be prevented by making a straight staple line that avoids crossing cartridge applications, has no narrow segments (particularly at the incisura angularis), is about 1 cm from the gastroesophageal junction, and has a squared-off final application. Generally speaking, leak is not prevented by sewing over the staple line or using staple line buttress material in the resection line. Leak is thought to be more a result of poor resultant stomach anatomy. Poor anatomy is a direct result of the shortcomings of the calibration equipment and technique used to create the staple line. Conventional calibration tubes specifically designed for use in a sleeve gastrectomy may provide some user benefits, but fail to reliably produce the proper geometry of the resultant anatomy from the vertical sleeve gastrectomy.
Accordingly, new apparatuses and methods are needed to address the shortcomings of existing apparatuses and methods. More particularly, improved apparatuses and methods are needed that improve the consistency and quality of the staple line created during a medical procedure, such as a vertical sleeve gastrectomy.